Enabling vehicles to navigate difficult terrain more effectively is a topic which has been researched both for terrestrial applications and applications in space. One concept that has been explored is the use of deployable structures to bridge gaps or traverse obstacles.
For example, many wheelchair users carry with them portable ramps which can be manually deployed to traverse small obstacles such as a single stair or a curb. However, such manual deployment can be difficult where mobility of the wheelchair user is restricted, and it is often difficult to secure the ramp in position to enable the wheelchair to pass over the ramp. In addition, retrieval of the ramp after the wheelchair has passed over it can also be difficult if there is limited room for manoeuvre of the wheelchair, coupled with the potential danger presented to the user if it is necessary to reach up or down a step to collect the ramp.
For other vehicle types, the manual deployment process can be cumbersome, particularly where multiple vehicle wheels need to be separately guided over one or more steps, and the ability to traverse particular terrain can be limited by the nature of the deployable structure which is used.
There is therefore a need for an improved mechanism for enabling vehicles to traverse particular terrain.
U.S. Pat. No. 7,850,189 discloses a portable ramp system intended to assist handicapped persons with transport in and out of houses and buildings. The system consists of a wheelchair attachment having several modular ramp members attached to one another to allow convenient access. The system requires manual deployment of the ramp, however, and as such requires the user to be physically capable of handling loads. Consequently, many users are unable to use this system. In addition, the system does not permit control over the extension of the connection arms between the wheelchair connection and the ramp, and the ramp length and associated ramp gradient limits the terrain over which the wheelchair can pass.
U.S. Pat. No. 5,447,317 discloses a lifting apparatus having two parallel base runners which attach to a wheelchair and serve as a lifting platform. The wheelchair is lifted relative to the base runners and a sliding subsystem moves the vehicle onto a particular step. The design is bulky and heavy, is limited to traversal of one or two steps, and is associated with potential balance issues.